As far as I know, it is necessary to multiply the focal length by the crop factor.
My Sony Nex 5 has a crop factor = 1.5
For lens Helios 77M-4 1.8/50 focal length will 50 * 1.5 = 75
Is this true for ...

Assuming I do want to take pictures of things like people, buildings and things further away, but not too far away. Does it sound reasonable to buy a 50-200 mm lens, when just considering the distance ...

I know next to nothing about cameras (other than how to push the shutter button). Up until a few days ago I thought of zoom as simply a multiple (e.g. my Canon S95 has 3 or 5X optical zoom) and had ...

I always have trouble getting sharper images from my 24-70 lens. I have watched numerous YouTube videos to correct this and its improved but not completely corrected. I am going on a trip and don’t ...

If I want to take a photo from about 600' away from my front door, and I want it to emulate what a person would see with unmagnified view, what mm would I set my camera lens length AND then what size ...

If I set a lens to, say, f/2 but my focus is set to its closest point, my effective f-number won't be f/2 any more but it will be higher by a factor that depends on focal length, image magnification ...

What is the best way to get two subjects in focus in a portrait (sometimes not at the same distance from the lens)? Obviously, this is a question of depth of field, but I am curious what some of the ...

85mm-135mm lenses are great for portraits because of compression perspective distortion, meaning they flatten facial features. However at those focal lengths, you have to step back a few meters from ...

If focal length is the measure between the rear element and the sensor then how can you have different flange focal distances? Is the focal length not literally the measure between the rear element ...

I have an image of a wall taken from a phone camera from a known height h from the ground.
Assume that the camera was held perfectly parallel to the wall and that the bottom of the image is perfectly ...

Is it the same if you take a picture setting 50mm with a 18-55mm lens and a 50mm f/1.8 prime lens? Assuming that ISO, aperture, and shutter speed are the same, will both the lens give same results?
I ...

I'm taking images of a light source in a scientific labratory, and I thought I had a good grasp on all these things, but now i'm second guessing myself after some results. The most important thing is ...

Why is there no apparent relation between focal length and physical lens size?
For example, the Nikkor 20mm lens has a physical length of 42.5mm! That's more than twice the focal length! And if you ...

1- I know different focal lengths change the depth and flatness of an objects in the picture. For examples longer focal lengths make objects appear flatter so they will be appropriate for portraits. ...

There are a lots of lenses for each camera and I understand that each lens caters to a different use case but my question is on how they arrive at these numbers.
For eg: there are prime lenses which ...

I'm looking to buy a compact camera, and having a very wide angle is important to me. I know that review sites often list the real focal length of the lens, but what I'm looking for is something that ...

Now, let me clarify (or...divulge) a few things.
I know cell phone cameras are generally wide angle, which makes sense because hey, people wanna go out to dinner, or a show, or at the park with their ...

Every lens has different focal length in terms of millimeter so if I have a 100mm lens, what does that refer to? Does it mean the length of the lens itself is going to be 4 inches long, or does this ...

Apparently multi-focal lenses such as the Tri-Elmar 16-18-21mm went out of fashion but I was wondering if the reasons for that were technical or commercial.
Are multi-focal harder to build compared ...